You forget that these people find the very existence of brown and black people exhausting. As a result, their stupid little safe space being full of political nonsense is still less stressful to them than the real world.
A quality shitpost is supposed to be offensive without punching down. It obviously achieves the first criterion for you. I would argue that the second criterion is also met because the offensive statement is immediately followed by self deprecation.
Ah, so the only thing we know with confidence is that it’s definitely not happening.